In data storage systems, digital data are written to and read from data storage surfaces. One type of data storage system is a disc drive, which reads and writes information along concentric tracks formed on discs. Read and write operations are performed through a transducer which is typically carried on a slider body. The slider and the transducer are sometimes collectively referred to as a head, and typically a single head is associated with each data storage surface. To locate a particular track on a disc, disc drives typically use embedded servo fields on the disc. These embedded fields are utilized by a servo subsystem to position a head over a particular track. In a disc drive, the servo subsystem includes a controller that is attached to the head to control its spatial position by moving it according to its input Position Error Signal (PES). The PES is etracted from a head output signal or readback signal with the help of a demodulator block or ciruit
As mentioned above, in a disc drive, a single head is typically associated with each data storage surface. Thus a disc drive demodulator needs to etract the PES from only a single readback signal. In the near future, manufactured data storage devices will include multiple probe heads (or tips), supported by a single arm, that read information from or write information to a data storage surface. At any given time, all or some of the tips will be active, resulting in more than one readback signal.
Thus, there is a need for a servo demodulation system that is that is capable of resolving multiple readback signals.